PURPOSE: To obtain homogeneous silica glass for an optical fiber at a high manufacturing speed by spraying sol prepared by hydrolyzing an alkyl silicate on a heating zone to form silica glass powder and by melting the powder with a flame.
CONSTITUTION: An alkyl silicate such as tetramethyl silicate is mixed with an alcohol such as methanol in about 1:9 volume ratio, and to the mixture is optionally added ≥1 kind of acid selected from phosphoric acid, stannic acid, plumbic acid, zincic acid, boric acid, titanic acid, aluminic acid and germanic acid or ≥1 kind of ester of such acid as a dopant material. Water is then added to prepare sol 2 by hydrolysis. The sol 2 in a container 3 is fed into the core tube 11 of a furnace provided with a heating element 10 as sol droplets 9 together with a compressed gas 8 from a spray nozzle 6 through a transfer pipe 4. In the tube 11 the droplets 9 are converted into gel, forming silica glass powder 14 in a container 13. The powder 14 is heat treated at about 800W 1,500°C and melted with a flame of oxygen and hydrogen to obtain transparent glass.
SUDA HIROYUKI
HANAWA FUMIAKI
NAKAHARA MOTOHIRO
